Page 46 - 2014 SDCA Project

PRELIMINARY BUILDING ENERGY SIMULATION

Passive House is a rigorous, yet elegantly simple, performance-based building certification program. Unlike, many building certification programs, Passive House requires that

the building meet stringent performance standards both before and after its construction and occupation. Achieving the performance metrics requires extensive project
planning, cross-team integrated design, and thorough execution of the design details. The Passive House concept and certification process was developed in a heating-

dominated climate zone, and its adoption in the United States is a fairly recent phenomenon, with few examples in warm-humid climate zones, providing a unique opportunity
for innovation. The core concept of Passive House is to tackle one of the largest sources of building energy usage, heating and cooling, by aggressively mitigating heating and
cooling loads produced by the building envelope.

Through super-insulation and superior air-tightness, Passive House structures deliver levels of efficiency that are simply not possible in conventional building designs.

Preventing heating and cooling loads is far simpler than designing systems of contraptions to efficiently—and nearly continuously—move heat between the interior and
exterior of the building. Improving the building envelope decreases the required heating and cooling capacity for a building’s HVAC design. However, the type of heat that must
be removed in the cooling season (cooling load) differs not only in magnitude—but also in composition. A building’s heating/cooling loads are comprised of three components:

Sensible heat: The heat that makes a thermometer change its reading

Latent heat: The heat contributed by the addition of water molecules to the air
Radiant heat: The heat from electromagnetic waves, such as sunlight

The sum of these three components of heat make up the building’s heating/cooling loads. Reducing the thermal conductance of the building envelope shifts the primary
source of cooling loads from the external environment to internal sources of heat gain. The largest contributors to internal cooling loads (heat gain) are occupants, along with

their need for contaminant-free air.

Currently, the best way to maintain vital indoor air quality is to throw out the contaminated “stale” air from inside a building and replace it with “fresh” outside air.

Maintaining healthy indoor air quality is essential for building occupants, but it carries a high thermal price during hot or cold weather. This is especially true during the cooling
season in a humid climate, where the air is moist and filled with invisible latent heat. Most cooling systems are designed primarily to remove sensible heat, and only remove

latent heat as a by-product of passing moist air over a cold coil. In a Passive House design, drying the moisture from the air is every bit as important as removing sensible heat
to drop the temperature.

44 SDCA